In patients with proteinuric renal diseases renal function almost invariably deteriorates, independent from the original renal disease. It has been demonstrated that the rapidity of renal function deterioration is determined by blood pressure and proteinuria1. Treatment modalities that lower proteinuria in general tend to attenuate the deterioration of renal function. As such, ACE-inhibitors have been proven to be of particular value in the treatment of patients with proteinuria, since these drugs consistently lower proteinuria. More recently, similar antiproteinuric effects have been described for the angiotensin receptor blockers (ARBs). Theoretically, ACE inhibitors may have advantages over ARBs because they are supposed to increase bradykinin levels. Bradykinin has also been implicated in the development of nephropathy in mice. About its role in human diabetic nephropathy few if any data exist. The effect of ACE inhibition or ARBs is not complete, since addition of either drug to the other may further improve albuminuria. This may be explained by insufficient dosage of single drug therapy or because of an escape phenomenon. The latter has been amply described for ACE inhibitors. Especially with chronic ACE inhibition angiotensin II levels may be near normal. This may lead to persistent angiotensin II effects, among which aldosterone stimulation.